Optical recording medium with an aluminum alloy metallic layer containing at least hafnium

ABSTRACT

In accordance with the present invention, there are provided information recording media having a substrate (2) and thereon a recording layer (3), and a metallic layer (4) composed of an aluminum alloy containing at least hafnium. The information recording media provided are excellent in corrosion resistance and also small in dependence of the recording power on linear velocity.

FIELD OF THE INVENTION

This invention relates to information recording media having a metalliclayer and more particularly to information recording media excellent incorrosion resistance or stability, and small in dependence of theirrecording power on linear velocity.

BACKGROUND OF THE INVENTION

In information recording media such as magnetooptical recording discscomprising a substrate and thereon a recording layer and a metalliclayer and capable of rewriting information, it is to be desired that thedependence of the recording power on linear velocity is made small sothat the recording power for recording information in said media doesnot largely vary with the inner peripheral and outer peripheral portionsof the medium.

Usually, in the information recording medium such as the magnetoopticalrecording disc, a metallic layer is formed, in addition to amagnetooptical recording layer, on a substrate. The metallic layerswhich have been used so far in the information recording media of thetype such as magnetooptical recording discs are composed of nickelalloys, aluminum metal or aluminum alloys containing 0.1-10% by weightof titanium. However, the metallic layers composed of aluminum metal oraluminum-titanium alloys had such a disadvantage that they are poor incorrosion resistance and cannot withstand a long term-service.

The metallic layers composed of nickel alloys had also such a seriousdisadvantage that the recording power required at the time of writinginformation in the information recording medium largely varies with theinner peripheral and outer peripheral portions of said medium, and thusthe dependence of the recording power on linear velocity is still large.

With the view of developing information recording media which areexcellent in corrosion resistance or longterm stability and which aresmall in linear dependence of the recording power on linear velocity,the present inventors prosecuted extensive researches to find that theinformation recording media having a metallic layer composed of analuminum alloy containing at least hafnium are excellent in corrosionresistance and small in dependence of the recording power on linearvelocity. Thus, the present invention has been accomplished.

OBJECT OF THE INVENTION

The present invention is intended to solve such problems associated withthe prior art as mentioned above, and an object of the invention is toprovide information recording media which are excellent in corrosionresistance and small in dependence of the recording power on linearvelocity.

SUMMARY OF THE INVENTION

The first information recording medium of the present invention whichhas a recording layer and a metallic layer on a substrate ischaracterized in that the metallic layer is composed of an aluminumalloy containing at least one element selected from among hafnium (Hf)and niobium (Nb) in an amount of 0.1-10 atom% based on all atomsconstituting aluminum alloy layer.

The second information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-9.5 atom% of hafnium and 0.1-5 atom% of chromium and 0.1-9.5 atomsconstituting aluminum alloy layer, the combined content of said hafniumand chromium being less than 10 atom%.

The third information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterizzedunit that the metallic layer is composed of an aluminum alloy containing0.1-9.5 atom% of hafnium, 0.1-5 atom% of chromium and 0.1-9.5 atom% oftitanium based on all atoms constituting aluminum alloy layer, thecombined content of said hafnium, chromium and titanium being less than10 atom%. constituting aluminum alloy layer, the combined content ofsaid hafnium and chromium being less than 10 atom%.

The third information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-9.5 atom% of hafnium, 0.1-5 atom% of chromium and 0.1-9.5 atom% oftitanium based on all atoms constituting aluminum alloy layer, thecombined content of said hafnium, chromium and titanium being less than10 atom%.

The fourth information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.5-5 atom% of hafnium and 0.5-5 atom% of titanium based on all atomsconstituting aluminum alloy layer, the combined content of said hafniumand titanium being 1-5.5 atom%.

The fifth information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-10 atom% of hafnium and 0.1-10 atom% of magnesium based on all atomsconstituting aluminum alloy layer, the combined content of said hafniumand magnesium being less than 15 atom%.

The sixth information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-10 atom% of hafnium, 0.1-10 atom% of magnesium and 0.1-10 atom% oftitanium based on all atoms constituting aluminum alloy layer, thecombined content of said hafnium, magnesium and titanium being less than15 atom%.

The seventh information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-10 atom% of hafnium, 0.1-10 atom% of magnesium and not more than 10atom% of chromium based on all atoms constituting aluminum alloy layer,the combined content of said hafnium, magnesium and chromium being lessthan 15 atom%.

The eighth information recording medium of the invention which has arecording layer and a metallic layer on a substrate is characterized inthat the metallic layer is composed of an aluminum alloy containing0.1-10 atom% of hafnium, 0.1-10atom% of magnesium, 0.1-10 atom% oftitanium and less than 10 atom% of chromium based on all atomsconstituting aluminum alloy layer, the combined content of said hafnium,magnesium, titanium and chromium being less than 15 atom%.

The information recording medium of the present invention as illustratedabove, which individually have a metallic layer composed of an aluminumalloy containing at least hafnium are excellent in corrosion resistance,small in the dependence of the recording power on linear velocity andexcellent in performance of protecting the recording layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough sketch of one embodiment of the information recordingmedium in cross section of the present invention.

FIG. 2 is a rough sketch of another embodiment of the informationrecording medium in cross section of the present invention.

1 . . . Information recording medium

2 . . . Substrate

3 . . . Recording layer

4 . . . Metallic layer

5 . . . Protective film

DETAILED DESCRIPTION OF THE INVENTION

The information recording media of the present invention are illustratedbelow in detail.

FIG. 1 is a rough sketch of the information recording medium in crosssection of one embodiment of the invention, and FIG. 2 is also a roughsketch of the information recording medium in cross section of anotherembodiment of the invention.

In the information recording media of the invention, the informationstored in said recording media is read out by means of light such aslaser beam. Information recording media of this type include, inconcrete, postscript type optical disc capable of additional recordingbut incapable of erasing information recorded, rewriting type opticaldiscs such as magnetooptical recording discs and phase change discs,capable of recording information as well as of erasing and reproducingthe information recorded.

As can be seen from FIG. 1, for example, in an information recordingmedium 1 of the invention, a recording layer 3 and a metallic layer 4are formed on a substrate 2 in that order.

Materials for the above-mentioned substrate 2 used in the invention arenot particularly limited to specific ones. However, when laser beam isincident upon the substrate 2 (from the direction of an arrow A), thematerials used therefor are preferably those which are transparent.Besides inorganic materials such as glass, aluminum and the like, suchtransparent materials include, for example, organic materials such aspoly(methyl methacrylate), polycarbonate, polymer alloys ofpolycarbonate with polystyrene, such cycloolefin random copolymers asdisclosed in U.S. Pat No. 4,614,778, such cycloolefin random copolymers(A) as mentioned below, poly-4-methyl-4-pentene, epoxy resins, polyethersulfone, polysulfone, polyether imide and the like. Of these organicmaterials, preferred are poly(methyl methacrylate), polycarbonate, suchcycloolefin random copolymers as disclosed in U.S. Pat. No. 4,614,778and the cycloolefin random copolymers (A) as mentioned below.

From the standpoint of good adhesion particularly to the recording layerand a small double refractive index, particularly desirable materialsfor the substrate used in the present invention are cycloolefin randomcopolymers (A) of ethylene and a cycloolefin represented by thefollowing general formula [I], [I-a] or [I-b]. ##STR1## wherein n is 0or a positive integer, R¹ to R² are the same or different, and eachrepresents a hydrogen atom, a halogen atom or a hydrocarbon group and R⁹to R¹², when taken together, may form a mono- or poly-cyclic hydrocarbonring which may optionally have double bond or bonds, or R⁹ and R¹⁰ orR¹¹ and R¹², when taken together, may form an alkylidene group.

Further explanation of the cycloolefin represented by the generalformula [I] will be given below. The cycloolefin represented by thegeneral formula [I] may also be represented by the following generalformula [I-a].

General formula ##STR2##

In the general formula [I-a], n is 0 or 1, m is 0 or positive integer,R¹ to R¹⁸ represent each a atom or a group selected from the group of ahydrogen atom, a halogen atom and a hydrocarbon group.

R¹⁵ to R¹⁸, when taken together, may form a mono- or poly-cyclichydrocarbon ring which may optionally have double bond or bonds.

Further more, R¹⁵ and R¹⁶, or R¹⁷ and R¹⁸, when taken together, may forman alkylidene group. ##STR3## wherein p is an integer of at least 0, qand r are each 0,1 or 2,R¹ to R¹⁵ represent each an atom or a groupselected from the group of a hydrogen atom, a halogen atom, an aliphatichydrocarbon group, an aromatic hydrocarbon group and an alkoxy group,and R⁵ (or R⁶) and R⁸ (or R⁷) may be bonded together directly without anintermediate group or through an alkylene group of one to three carbonatoms.

The concrete example of the cycloolefins represented by the generalformula [I] includes1,4,5,8-dimethano-1,2,3,4,4a,5,8,8aoctahydronaphthalene, such octahydronaphthalenes as2-methyl-1,4,5,8-dimethano1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-ethyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-propyl1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-hexyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2,3-dimethyl-1,4,5,8-dimethano,-1,2,3,4,4a,5,8,8a-octahydronaphthalene,1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-methyl-3-ethyl1,4,5,8,-dimethano-1,2,3,4,4a,5,8,8aoctahydronaphthalene,2-chloro-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8aoctahydronaphthalene,2-bromo-1,4,5,8-dimethano1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-fluoro-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalne,2-isobutyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-cyclohexyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octanhydronaphthalene,2-n-butyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,2-isobutyl-1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octahydronaphthalene,etc.

Furthermore, the cycloolefin represented by the general formula [I]includes, bicyclo[2,2,1] hepto-2-en derivatives,tetracyclo[4,4,0,12.5,17.]-3-dodecene derivatives,hexacyclo[6,6,1³.6,1¹¹⁰.13,0².7,0⁹.14 ]-4- heptadesene, derivaties,

octacyclo[8,8,0,1².9,1⁴.7, 1¹¹.18, 1¹³.16, 0³.8,0¹².17 ]-5-docosenederivatives,

pentacyclo[8,8,0,1².9,1⁴.7,1¹¹.18 1¹³.16, 0³.8,0¹².17 ]-5docosenederivatives,

pentacyclo[6,6,1,1³.6,0².7,0⁹.14 ]-4-hexadecene derivatives,heptacyclo-5-icosene derivatives,

heptacyclo-5-henicosene derivatives, toricyclo[4,3,0,1².5 ]-3-decenederivatives toricyclo[4,3,0,12.5]-3-undecene derivatives,pentacyclo[6,5,1,13.6,02.7,09.13]-4-pentadecene derivatives,pentacyclopentadecadiene derivatives,

pentacyclo[4,7,0,1².5,0⁸.13,1⁹.12 ]-4icosene derivatives,pentacyclo[7,8,0,1³.6,0².7,1¹⁰.17,011.16,1¹².15 ]-4-icosene derivatives,and

nonacyclo[9,10,1,1,4.7,0³.8,0².10 0¹².21,1¹³.20,0¹⁴.19 1¹⁵.18]-5-pentacosene derivatives.

The concrete examples of such componds as mentioned above areillustrated hereunder.

Bicyclo[2,2,1]hept-2-ene derivatives such as:

    ______________________________________                                         ##STR4##     Bicyclo[2,2,1]hept-2-ene                                         ##STR5##     6-Methylbicyclo[2,2,1]hept-2-ene                                 ##STR6##     5,6-Dimethylbicyclo[2,2,1]hept-2-ene                             ##STR7##     1-Methylbicyclo[2,2,1]hept-2-ene                                 ##STR8##     6-Ethylbicyclo[2,2,1]hept-2-ene                                  ##STR9##     6-n-Butylbicyclo[2,2,1]hept-2-ene                                ##STR10##    6-Isobutylbicyclo[2,2,1]hept-2-ene                               ##STR11##    7-Methylbicyclo[2,2,1]hept-2-ene:                               ______________________________________                                    

Tetracyclo[4,4,0,1².5,1⁷.10 ]-3-dodecene derivatives such as:

    ______________________________________                                         ##STR12##         Tetracyclo[4,4,0,1.sup.2.5,1.sup.7.10 ]-3- dodecene         ##STR13##         5,10-Dimethyltetracyclo [4,4,0,1.sup.2.5,1.sup.7.10                           ]-3-dodecene                                                ##STR14##         2,10-Dimethyltetracyclo- [4,4,0,1.sup.2.5,1.sup.7.10                          ]-3-dodecene                                                ##STR15##         11,12-Dimethyltetracyclo- [4,4,0,1.sup.2.5,1.sup.7.10                         ]-3-dodecene                                                ##STR16##         2,7,9-Trimethyltetracyclo- [4,4,0,1.sup.2.5,1.sup.7.10                        ]-3-dodecene                                                ##STR17##         9-Ethyl-2,7-dimethyltetra- cyclo-[4,4,0,1.sup.2.5,1.sup                       .7.10 ]-3- dodecene                                         ##STR18##         9-Isobutyl-2,7-dimethyltetra- cyclo-[4,4,0,1.sup.2.5,1.                       sup.7.10 ]-3- dodecene                                      ##STR19##         9,11,12-Trimethyltetracyclo- [4,4,0,1.sup.2.5,1.sup.7.1                       0 ]-3-dodecene                                              ##STR20##         9-Ethyl-11,12-dimethyltetra- cyclo-[4,4,0,1.sup.2.5,1.s                       up.7.10 ]-3- dodecene                                       ##STR21##         9-Isobutyl-11,12-dimethyl- tetracyclo-[4,4,0,1.sup.2.5,                       1.sup.7.10 ]-3- dodecene                                    ##STR22##         5,8,9,10-Tetramethyltetra- cyclo-[4,4,0,1.sup.2.5,1.sup                       .7.10 ]-3- dodecene                                         ##STR23##         8-Methyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                                ]-3-dodecene                                                ##STR24##         8-Ethyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10 ]-3-dodec                       ene                                                         ##STR25##         8-Propyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                                ]-3-dodecene                                                ##STR26##         8-Hexyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10 ]-3-dodec                       ene                                                         ##STR27##         8-Stearyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                               ]-3-dodecene                                                ##STR28##         8,9-Dimethyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                            ]-3-dodecene                                                ##STR29##         8-Methyl-9-ethyltetracyclo [4,4,0,1.sup.2.5,1.sup.7.10                        ]-3-dodecene                                                ##STR30##         8-Chlorotetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                                ]-3-dodecene                                                ##STR31##         8-Bromotetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10 ]-3-dodec                       ene                                                         ##STR32##         8-Fluorotetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                                ]-3-dodecene                                                ##STR33##         8,9-Dichlorotetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                            ]-3-dodecene                                                ##STR34##         8-Cyclohexyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                            ]-3-dodecene                                                ##STR35##         8-Isobutyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10                              ]-3-dodecene                                                ##STR36##         8-Butyltetracyclo[4,4,0, 1.sup.2.5,1.sup.7.10 ]-3-dodec                       ene                                                         ##STR37##         8-Ethylidenetetracyclo[4,4,0, 1.sup.2.5 1,.sup.7.10                           ]-3-dodecene                                                ##STR38##         8-Ethylidene-9-methyltetra- cyclo[4,4,0,1.sup.2.5,1.sup                       .7.10 ]-3- dodecene                                         ##STR39##         8-n-Propylidene-9-ethyltetra- cyclo[4,4,0,1.sup.2.5,1.s                       up.7.10 ]-3- dodecene                                       ##STR40##         8-Ethylidene-9-isopropyltetra- cyclo[4,4,0,1.sup.2.5,1.                       sup.7.10 ]-3- dodecene                                      ##STR41##         8-Ethylidene-9-butyltetra- cyclo[4,4,0,1.sup.2.5,1.sup.                       7.10 ]-3- dodecene                                          ##STR42##         8-n-Propylidenetetracyclo [4,4,0,1.sup.2.5,1.sup.7.10                         ]-3-dodecene                                                ##STR43##         8-n-Propylidene-9-ethyltetra- cyclo[4,4,0,1.sup.2.5,1.s                       up.7.10 ]-3- dodecene                                       ##STR44##         8-Ethylidene-9-ethyltetra- cyclo[4,4,0,1.sup.2.5,1.sup.                       7.10 ]-3- dodecene                                          ##STR45##         8-n-Propylidene-9-isopropyl- tetracyclo[4,4,0,1.sup.2.5                       ,1.sup.7.10 ]-3- dodecene                                   ##STR46##         8-n-Propylidene-9-butyltetra- cyclo[4,4,0,1.sup.2.5,1.s                       up.7.10 ]-3- dodecene                                       ##STR47##         8-Isopropylidenetetracyclo [4,4,0,1.sup.2.5,1.sup.7.10                        ]-3-dodecene                                                ##STR48##         8-Isopropylidene-9-methyl- tetracyclo[4,4,0,1.sup.2.5,1                       .sup.7.10 ]-3- dodecene                                     ##STR49##          8-Isopropylidene-9-ethyl- tetracyclo[4,4,0,1.sup.2.5,1                       .sup.7.10 ]-3- dodecene                                     ##STR50##         8-Isopropylidene-9-isopropyl- tetracyclo[4,4,0,1.sup.2.                       5,1.sup.7.10 ]-3- dodecene                                  ##STR51##         8-Isopropylidene-9-butyl- tetracyclo[4,4,0,1.sup.2.5,1.                       sup.7.10 ]-3- dodecene                                     ______________________________________                                    

Hexacyclo[6,6,1,1³.6,1¹⁰.13,0².7,0⁹.14 ]-4-heptadecene derivates suchas:

    ______________________________________                                         ##STR52##      Hexacyclo[6,6,1,1.sup.3.6,1.sup.10.13,0.sup.2.7,0.sup.9.14                     ]- 4-heptadecene                                              ##STR53##      12-Methylhexacyclo[6,6,1,1.sup.3.6, 1.sup.10.13                               ,0.sup.2.7,0.sup.9.14 ]-4-heptadecene                          ##STR54##      12-Ethylhexacyclo[6,6,1,1.sup.3.6, 1.sup.10.13,0.sup.2.7,0                    .sup.9.14 ]-4-heptadecene                                      ##STR55##      12-Isobutylhexacyclo[6,6,1,1.sup.3.6, 1.sup.10.13,0.sup.2.                    7,0.sup.9.14 ]-4-heptadecene                                   ##STR56##      1,6,10-Trimethyl-12-isobutyl- hexacyclo[6,6,1,1.sup.3.6,1.                    sup.10.13,0.sup.2.7,0.sup.9.14 ]- 4-heptadecene               ______________________________________                                    

Octacyclo[8,8,0,1².9,1⁴.7,1¹¹.18,1¹³.16,0³.8,0.sup.12.17 ]-5-docosenderivatives such as:

    ______________________________________                                         ##STR57##      Octacyclo[8,8,0,1.sup.2.9,1.sup.4.7,1,.sup.11.18,                             1.sup.13.16,0.sup.3.8,0.sup.12.17 ]-5-docosene                 ##STR58##      15-Methyloctacyclo[8,8,0,1.sup.2.9,1.sup.4.7, 1,.sup.11.18                    ,1.sup.13.16,0.sup.3.8,0.sup.12.17 ]-5-docosene                ##STR59##      15-Ethyloctacyclo[8,8,0,1.sup.2.9,1.sup.4.7, 1,.sup.11.18,                    1.sup.13.16,0.sup.3.8,0.sup.12.17 ]-5-docosene:               ______________________________________                                    

pentacyclo[6,6,1,1³.6,0².7 0⁹.14 ]-4-hexadecene derivatives such as:

    ______________________________________                                         ##STR60##       Pentacyclo[6,6,1,1.sup.3.6,0.sup.2.7,0.sup.9.14 ]-4-                          hexadecene                                                    ##STR61##       1,3-Dimethylpentacyclo[6,6,1, 1.sup.3.6,0.sup.2.7,0.sup.9                     .14 ]-4-hexadecene                                            ##STR62##       1,6-Dimethylpentacyclo[6,6,1, 1.sup.3.6,0.sup.2.7,0.sup.9                     .14 ]-4-hexadecene                                            ##STR63##       15,16-Dimethylpentacyclo[6,6,1, 1.sup.3.6,0.sup.2.7,0.sup                     .9.14 ]-4-hexadecene                                         ______________________________________                                    

heptacyclo-5-icosene derivatives or heptacyclo-t-henicosene derivativessuch as:

    ______________________________________                                         ##STR64##     Heptacyclo[8,7,0,1.sup.2.9,1.sup.4.7,1.sup.11.17, 0.sup.3.8                   ,0.sup.12.16 ]-5-icosene                                        ##STR65##     Heptacyclo[8,8,0,1.sup.2.9,1.sup.4.7,1.sup.11.18, 0.sup.3.8                   ,0.sup.12.17 ]-5-henicosene                                    ______________________________________                                    

toricyclo[4,3,0,1².5 ]-3-decene derivatives such as:

    ______________________________________                                         ##STR66##    Tricyclo[4,3,0,1.sup.2.5 ]-3-decene                              ##STR67##    2-Methyl-tricyclo[4,3,0,1.sup.2.5 ]-3-decene                     ##STR68##    5-Methyl-tricyclo[4,3,0,1.sup.2.5 ]-3- decene:                  ______________________________________                                    

tricyclo[4,4,0,1².5 ]-3undecene derivatives such as:

    ______________________________________                                         ##STR69##      Tricyclo[4,4,0,1.sup.2.5 ]-3-undecene                          ##STR70##      10-Methyl-tricyclo[4,4,0,1.sup.2.5 ]- 3-undecene:             ______________________________________                                    

pentacyclo[6,5,1,1³.6,0².7 0⁹.13 ]-4-pentadecene derivatives such as:

    ______________________________________                                         ##STR71##       Pentacyclo[6,5,1,1.sup.3.6, 0.sup.2.7,0.sup.9.13                              ]-4-pentadecene                                               ##STR72##       1,3-Dimethylpentacyclo[6,5,1,1.sup.3.6, 0.sup.2.7,0.sup.9                     .13 ]-4-pentadecene                                           ##STR73##       1,6-Dimethylpentacyclo[6,5,1,1.sup.3.6, 0.sup.2.7,0.sup.9                     .13 ]-4-pentadecene                                           ##STR74##       14,15-Dimethylpentacyclo[6, 5,1,1,.sup.3.6 ,0.sup.                            2.7,0.sup.9.13 ]-4-pentadecene:                              ______________________________________                                    

diene compounds such as:

    ______________________________________                                         ##STR75##       Pentacyclo[6,5,1,1.sup.3.6, 0.sup.2.7,0.sup.9.13                              ]-4,10-pentadecadiene:                                       ______________________________________                                    

Pentacyclo[7,4,0,1².5,0⁸.13,1⁹.12 ]-3-pentadecene derivatives such as:

    ______________________________________                                         ##STR76##       Pentacyclo[7,4,0,1.sup.2.5,0.sup.8.13,1.sup.9.12 ]-3-                         pentadecene                                                   ##STR77##       Methyl-substituted pentacyclo [7,4,0,1.sup.2.5,0.sup.8.13                     ,1.sup.9.12 ]-3-pentadecene                                  ______________________________________                                    

heptacyclo[8,7,0,1³.6,0².7,1¹⁰.17,0¹¹.16,1¹².15 ]-4icosene derivativessuch as:

    ______________________________________                                         ##STR78##      Heptacyclo[8,7,0,1.sup.3.6,0.sup.2.7,1.sup.10,17,                             0.sup.11.16,1.sup.12.15 ]-4-icosene                            ##STR79##      Dimethyl-substituted heptacyclo [8,7,0,1.sup.3.6,0.sup.2.7                    ,1.sup.10,17,0.sup.11.16,1.sup.12.15 ]-4- icosene             ______________________________________                                    

nonacyclo[10,9,1,1⁴.7,0³.8,0².10 0¹².21,1¹³.20,0¹⁴.19,1¹⁵.18]5-pentacosene derivatives such as:

    ______________________________________                                         ##STR80##      Nonacyclo[10,9,1,1.sup.4.7,0.sup.3.8,0.sup.2.10,0.sup.12.2                    1, 1.sup.13.20,0.sup.14.19,1.sup.15.18 ]-5-pentacosene         ##STR81##      Trimethyl-substituted nonacyclo [10,9,1,1.sup.4.7,0.sup.3.                    8,0.sup.2.10,0.sup.12.21,1.sup.13.20, 0.sup.14.19,1.sup.15                    .18 ]-5-pentacosene                                           ______________________________________                                    

The following compounds can be mentioned as concrete examples ofcycloolefins represented by the formula [I-b].

    ______________________________________                                         ##STR82##       5-Phenylbicyclo[2,2,1]hept-2-ene                              ##STR83##       5-Methyl-5-phenylbicyclo[2,2,1] hept-2-ene                    ##STR84##       5-Benzylbicyclo[2,2,1]hept-2-ene                              ##STR85##       5-Tolybicyclo[2,2,1]hept-2-ene                                ##STR86##       1,4-Methanol-1,1a,4,4a- tetrahydrofluorene                    ##STR87##       1,4-Methano-1,4,4a,5,10,10a- hexahydroanthracene              ##STR88##       Cyclopentadiene-acenaphthylene addition products              ##STR89##       5-(α-naphthyl)bicyclo[2,2,1]hept-  2-ene               ______________________________________                                    

The cycloolefin random copolymers (A) comprise ethylene units and theabove-mentioned cycloolefin units as the essential components asaforesaid, however, if necessary, in addition to these two essentialcomponents, said copolymers may contain other copolymerizableunsaturated monomer components so long as they will not throwhinderances in the way of accomplishing the object of the presentinvention. The unsaturated monomers which may be copolymerized, ifnecessary, with the copolymers (A) may include,for example,alpha-olefins having from 3 to 20 carbon atoms such as propylene,1-butene, 4-methyl-1pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene,1tetradecene, 1-hexadecene, 1-octadecene and 1-eicosene which may beused in an amount of up to an equimolar to the ethylene component unitin the resulting random copolymer.

In the cycloolefin random copolymer [A] having a softening point (TMA)of at least 70° C., the recurring units [a] derived from ethylene arepresent in an amount of from 40 to 85 mol%, preferably from 50 to 75mol%, while the recurring units [b] derived from the cycloolefin arepresent in an amount of from 15 td 60 mol%, preferably from 25 to 50mol%, and these recurring units [a] and [b] are arranged at random inthe substantially linear chain of the copolymer [A]. The molarpercentage of the recurring units [a] and [b] were determined by ¹³C-NMR. The fact that this cycloolefin random copolymer [A]is completelysoluble in decalin at 135° C. confirms that it is substantially linearand free from a gel-forming crosslinked structure.

The cycloolefin random copolymer [A] has an intrinsic viscosity [η] offrom 0.05 to 10 dl/g, preferably from 0.08 to 5 dl/g as measured indecalin at 135° C.

The softening temperature (TMA) of the cycloolefin random copolymer [A]as measured by a thermal mechanical analyzer is at least 70° C.,preferably from 90 to 250° C., and further preferably from 100 to 20° C.The softening temperature (TMA) referred to above was determined bymonitoring thermal deformation behavior of a 1 mm sheet of the copolymer[A] using a thermomechanical analyzer manufactured and sold by Du Pont.More specifically, a quartz needle was vertically placed on the sheetunder a load of 49 g and the assembly was heated at a rate of 5° C./min,and a temperature at which the needle penetrated into the sheet by thedepth of 0.635 mm was taken as TMA. This cycloolefin random copolymer[A]has a glass transition temperature (Tg) of normally from 50° to 230°C., preferably from 70° to 210° C.

The crystallinity of this cycloolefin random copolymer [A] as measuredby X-ray diffractometry is normally from 0 to 10%, preferably from 0 to7%, and further preferably from 0 to 5%.

The cycloolefin copolymers (A) constituting the cycloolefin randomcopolymer composition used in the present invention for forming thesubstrate may all be prepared by the processes proposed by the presentinventors in Japanese Patent L-O-P Publns. Nos. 168708/1985,120816/1986, 115912/1986 and 115916/1986, 252406/1987, 252407/1987,271308/1986 and 272216/1986, while suitably selecting the conditions.

Furthermore, in the present invention, there may also be used as thesubstrate material a cycloolefin random copolymer composition comprisinga cycloolefin random copolymer [A] prepared by copolymerizing ethylenewith a cycloolefin represented by the following formula [I], [I-a] or[I-b] and having an intrinsic viscosity [η] of 0.05-10 dl/g measured indecalin at 135° C. and a softening temperature (TMA) of at least 70° C.,and a cycloolefin random copolymer [B]prepared by copolymerizingethylene with a cycloolefin represented by the formula [I], [I-a] or[I-b] and having an intrinsic viscosity [η] of 0.05-5 dl/g measured indecalin at 135° C. and a softening temperature (TMA) of less than 70° C.

Furthermore, the substrate of the magnetooptical recording mediaaccording to the invention may be made of polymers having recurringunits of the general formula [III] resulting from ring opening of thecycloolefin monomers [I], or polymers having recurring units of thegeneral formula [IV] resulting from hydrogenation of the units [III].##STR90## In the general formula [III] or [IV], n and R¹ to r¹² are asdefined in the general formula [I].

A thickness of the substrate, though not particularly limited, ispreferably 0.5-5 mm and especially 1-2 mm.

In the invention, materials for the recording layer 3 are notparticularly limited to specific ones. However, when the substrate 3used is a magnetooptical recording layer having a monoaxial anosotropyperpendicular to the layer surface, this recording layer 3 is preferablycomposed of at least one member selected from among (i) 3d transitionmetals and at least one element selected from among (iii) rare earthelements, or composed of at least one member selected from among (i) 3dtransition metals, (ii) a corrosion-resistant metal, and at least oneelement selected from among (iii) rare earth elements.

The 3d transition metals used include Fe, Co, Ti, V, Cr, Mn, Ni, Cu andZn. Of these metals, preferred is Fe or Co, or are both of them.

The corrosion-resistant metal (ii) is capable of improving oxidationresistance of this magnetooptical recording layer as the recording layer3 by incorporation into this recording layer 3 of saidcorrosion-resistant metal. Such corrosion-resistant metal used includesPt, Pd, Ti, Zr, Ta, Mo, Nb and Hf. Of these metals, preferred are Pt, Pdand Ti, and particularly Pt or Pd, or both of them.

The rate earth elements (iii) used include, for example, Gd, Tb, Dy, Ho,Er, Tm, Yb, Lu, La, Ce, Pr, Nd, Pm, Sm and Eu. Of these elements,preferred are Gd, Tb, Dy, Ho, Nd, Sm and Pr.

Such magnetooptical recording layer as mentioned above desirablycontains the 3d transition metal (i) in an amount of 30-85 atom%,preferably 40-70 atom%, the corrosion-resistant metal (ii) in an amountof less than 30 atom%, preferably 5-25 atom%, and the rare earth element(iii) in an amount of 5-50 atom%, preferably 25-45 atom%.

When the recording layer 3 used is other than the magnetoopticalrecording layer, for example, said recording layer is a phase changetype recording layer, this recording layer 3 is composed of such analloy film, for example, as consisting essentially of Te or Se, and ofTe-Ge-Sb alloy film, In-Sb-Te alloy film Te-Ge-Cr alloy film or Te-Ge-Znalloy film. Further an organic dye film composed of polymethinecompounds or cyanine compounds may also be used as the phase change typerecording layer.

A thickness of the recording layer 3, though not particularly limited,is 50-5000 Å, preferably 100-2000 Å.

In the first information recording medium of the present invention, themetallic layer is formed from an aluminum alloy containing 0.1-10 atom%of at least one element (metal) selected from among hafnium and niobium.

Concretely, the metallic layer 4 is composed of an aluminum alloycontaining 0.114 10 atom%, preferably 1-6 atom% of hafnium (Hf), analuminum alloy containing 0.1-10 atom%, preferably 1-6 atom% of niobium(Nb), or of an aluminum alloy containing both hafnium and niobium in anamount totaling to 0.1-10 atom%.

The metallic layer 4-as mentioned above may contain small amounts of atleast one of other metals (elements) in addition to aluminum, hafniumand/or niobium. Such other metal as mentioned above include, forexample, chromium (Cr, only in case of Al-Nb alloy), silicon (Si),tantalum (Ta), copper (Cu), tungsten (W), zirconium (Zr), manganese(Mn), magnesium (Mg, only in case of Al-Nb alloy) and vanadium (V). Theamount of these other metals contained, if any, in the metallic layer isusually less than 5 atom%, preferably less than 2 atom%.

In the second information recording medium of the invention, themetallic layer is formed from an aluminum alloy containing 0.1-9.5atom%, preferably 1-5 atom% of hafnium and 0.1-5 atom%, preferably 1-3atom% of chromium.

In this aluminum alloy, the combined content of hafnium and chromium ispreferably less than 10 atom%.

In the third information recording medium of the invention, the metalliclayer is formed from an aluminum alloy containing 0.1-9.5 atom%,preferably 1-5 atom% of hafnium, 0.1-5 atom%, preferably 1-3 atom% ofchromium and 0.1-9.5 atom%, preferably 1-5 atom% of titanium.

In this aluminum alloy, the combined content of hafnium, chromium andtitanium is preferably less than 10 atom%.

The metallic layers of the second and third information recording mediaof the invention as illustrated above may also contain, in addition tothe aluminum, hafnium, chromium and titanium, small amounts of at leastone of other elements (metals). Such other elements (metal) include, forexample, silicon (Si),tantalum (Ta), copper (Cu), tungsten (W),zirconium (Zr), manganese (Mn), and vanadium (V). The amount of theseother elements (metals) contained, if any, in the metallic layer isusually less than 5 atom%, preferably less than 2 atom%.

In the fourth information recording medium of the invention, themetallic layer is formed from an aluminum alloy containing 0.5-5 atom%,preferably 1-3 atom% of hafnium, and 0.5-5 atom%, preferably 1-3 atom%of titanium.

In this aluminum alloy, the combined content of hafnium and titanium is1-5.5 atom%, preferably 2-4 atom%.

The metallic layer of the fourth information recording medium of theinvention as illustrated above may also contain, in addition toaluminum, hafnium and titanium, small amounts of at least one of otherelements (metals). Such other elements (metals) include, for example,silicon (Si), tantalum (Ta), copper (Cu), tungsten (W), zirconium (Zr),manganese (Mn), and vanadium (V). The amount of these other elements(metals) contained, if any, in the metallic layer is usually less than 5atom%, preferably less than 2 atom%.

In the fifth information recording medium of the invention, the metalliclayer is formed from an aluminum alloy containing 0.1-10 atom%,preferably 1-5 atom% of, hafnium and 0.1-10 atom%, preferably 1-5 atom%of magnesium.

In this aluminum alloy, the combined content of hafnium and magnesium isless than 15 atom%, preferably 1- atom%.

In the sixth information recording medium of the invention, the metalliclayer is formed from an aluminum alloy containing 0.1-10 atom%,preferably 1-5 atom% of hafnium, 0.1-10 atom%, preferably 1-5 atom% ofmagnesium and 0.1-10 atom%, preferably 1-5 atom% of titanium.

In this aluminum alloy, the combined content of hafnium, magnesium andtitanium is desirably less than 15 atom%, preferably 1-10 atom%.

In the seventh information recording medium of the invention, themetallic layer is formed from an aluminum alloy containing 0.1-10 atom%,preferably 1-5 atom% of hafnium, 0.1-10 atom%, preferably 1-5 atom% ofmagnesium and not more than 10 atom%, preferably 0.1-10atom%, morepreferably 1-5 atom% of chromium.

In this aluminum alloy, the combined content of hafnium, magnesium andchromium is desirably less than 15 atom%, preferably 1-10 atom%.

In the eighth information recording medium of the invention, themetallic layer is formed from an aluminum alloy containing 0.1-10 atom%,preferably 1-5 atom% of hafnium, 0.1-10 atom%, preferably 1-5 atom% ofmagnesium, less than 10 atom%, preferably 1-5 atom% of chromium and0.1-10 atom%, preferably 1-5 atom% of titanium.

In this aluminum alloy, the combined content of hafnium, magnesium,chromium and titanium is desirably less than 15 atom%, preferably 1-10atom%.

In the fifth, sixth, seventh and eighth information recording media ofthe invention as illustrated above, the metallic layers may each containsmall amounts of at least one of other elements (metals) in addition tohafnium, magnesium, titanium and chromium. Such small amounts of otherelements (metals) include, for example, silicon (Si), tantalum (Ta),copper (Cu), tungsten (W), zirconium (Zr), manganese (Mn) and vanadium(V). The amount of such other elements (metals) contained, if any, inthe metallic layer is usually less than 5 atom%, preferably less than 2atom%.

A thickness of the above-mentioned metallic layers is 100-5000 Å,preferably 500-3000 Å and especially 700-2000 Å.

The metallic layers used in the present invention fulfil their functionas good heat conductive layers, and in the presence of these metalliclayers, the center portion of pits formed in the recording layers may beprevented from being excessively heated to high temperature by theaction of the recording laser beam applied thereto. As the result, it isconsidered that the dependence of the information recording media of theinvention on linear velocity is made small.

The metallic layers of the invention which are also excellent incorrosion resistance have such a characteristic feature that thedependence of the information recording media on linear velocity issmall even after being used for a long period of time, and that saidmetallic layers are excellent in performance of protecting the recordinglayers.

The structure of the information recording media of the invention shownin FIG. 1 is given by way of illustration but not of limitation. Forinstance, they may be prepared by providing a protecting film (enhancingfilm) 5 on the aforementioned substrate 5 and then providing further therecording layer 3 and the metallic layer 4 in that order. The protectivefilm (enhancing film) 5 is formed desirably from Si₃ N₄, SiN_(x)(0<x<4/3), AlN, ZnSe, ZnS, Si or CdS, though not limited thereto. Athickness of this protective film is 100-2000 Å, preferably about500-1500 Å. Of these materials used for forming the protective film,particularly preferred are Si₃ N₄ and SiNx (0<x<4/3) from a viewpoint ofcrack resistance.

The function of the protective film is to protect the recording layerand, at the same time, it enhances the information recording medium insensitivity and functions as an enhancing film. Such a protective layerdesirably has a refractive index larger than that of the substrate.

The information recording media of the present invention may be preparedby forming on the substrate the recording layer and the metallic layerand, if necessary, the protective layer using such film-forming methods,for example, vacuum deposition, sputtering, electron beam deposition orthe like.

EFFECT OF THE INVENTION

The information recording media of the present invention comprising themetallic layer composed of a specific aluminum alloy are excellent incorrosion resistance, small in the dependence of the recording power onlinear velocity and in performance of protecting the recording layer.

The present invention is illustrated below with reference to examples,but it should be construed that the invention is in no way limited tothose examples.

The term "optimum recording power" used in the following Examplesdesignates a recording power with which writing signals at a frequencyof 1 MHz and a duty factor of 50% are recorded and which makes minimumthe secondary harmonics of signals reproduced from the recorded signals.Recording media show a lower degree of dependence on the linear velocitywhen the information recording media show smaller difference of theoptimum recording powers determined at different linear velocities.

EXAMPLE 1

Hereinafter, corrosion resistance of the metallic layer was examinedfirst by the following procedure.

On a glass substrate, a metallic layer composed of an aluminum-hafniumalloy was deposited to a thickness of 700 Å by the sputtering processusing an aluminum-hafnium composite target. The hafnium content in theabove-mentioned aluminum-hafnium alloy (layer) constituting the metalliclayer as formed was 4 atom% and the alumium content was 96 atom%.

This metallic layer as formed was immersed for 4 hours at 60° C. in anaqueous solution containing 10% by weight of sodium chloride, wherebythe corrosion resistance of the metallic layer was evaluated bymeasuring a change in reflectance of said metallic layer.

The reflectance of the metallic layer did not change before and afterthe immersion in the sodium chloride aqueous solution of said metalliclayer.

EXAMPLE 2

On a glass substrate, a metallic layer composed of an aluminum-niobiumalloy was deposited to a thickness of 700 Å by the sputtering processusing an aluminum-niobium composite target. The niobium content in thealuminum-niobium alloy (layer) constituting the metallic layer as formedwas 4 atom%.

This metallic layer was immersed four hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride, whereby thecorrosion resistance of the metallic layer was evaluated by measuring achange in reflectance of said metallic layer.

The reflectance of the metallic layer did not change before and afterthe immersion in the sodium chloride aqueous solution of said metalliclayer.

Comparative Example 1

On a glass substrate, a metallic layer composed of aluminum wasdeposited to a thickness of 700 Å by the sputtering process using analuminum target.

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride, whereby corrosionresistance of the metallic layer was evaluated by measuring a change inreflectance of said metallic layer.

The reflectance of the metallic layer measured after the immersion inthe aqueous sodium chloride solution of said metallic layer was lower byabout 30% than that measured before said immersion.

EXAMPLE 3

On a disk substrate composed of an amorphous copolymer of ethylene with1,4,5,8-dimethano-1,2,3,4,4a,5,8,8a-octanhydronaphthalene (structureformula: ##STR91## abbreviated to DMON hereinafter), the amorphouscopolymer having 59 mol% of an ethylene unit content determined by NMRanalysis, an intrinsic viscosity [η] of 0.42 dl/g measured in decalin at135° C. and a softening temperature (TMA) of 154° C., were depositedsuccessively a protective film composed of Si₃ N₄ to a thickness of 1100Å and a recording layer composed of Pt₁₀ Tb₂₉ Fe₅₅ Co₆ (atom%) to athickness of 260 Å by the sputtering process, and thereon was depositeda metallic layer composed of an aluiminum-hafnium alloy to a thicknessof 700 Å by the sputtering process using an aluminum-hafnium compositetarget. The hafnium content in the aluminum-hafnium alloy (layer)constituting the metallic layer was 4 atom% and the aluminum content was96 atom%.

The information recording medium thus obtained was held for about 720hours under the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer for the recording layer were evaluated bymeasuring a change in reflectance of said information recording medium.

The reflectance of the information recording medium did not changebefore and after holding said metallic layer under the circumstances of80° C. and a relative humidity of 85%.

This fact means that the metallic layer are excellent in corrosionresistance and in performance of protecting the recording layer.

EXAMPLE 4

Example 3 was repeated except that the metallic layer formed had athickness of 500 Å.

The information recording medium obtained was held for about 720 hoursunder the circumstances of 80° C. and a relative humidity of 85% tomeasure reflectance of said information recording medium, whereby thereflectance of said information recording medium did not change.

The optimum recording power of this information recording medium at alinear velocity of 5.7 m/sec was 3.7 mW, and the optimum recording powerat a linear velocity of 11.3 m/sec was 5.2 mW.

Comparative Example 2

On a substrate used in Example 3, were deposited successively aprotective film composed of Si₃ N₄ and a recording layer composed ofPt₁₀ Tb₂₉ Fe₅₅ co₆ (atom %) by the sputtering process, and thereon wasdeposited a metallic layer composed of aluminum to a thickness of 700 Åby the sputtering process using an aluminum target.

The information recording medium thus obtained was held for about 720hours under the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer for the recording layer were evaluated bymeasuring a change in reflectance of said information recording medium.

The reflectance of said information recording medium measured afterholding said recording medium was lower by about 15% than that measuredbefore said holding.

Example 5

Hereinafter, corrosion resistance of a metallic layer composed of analuminum-halfnium-chromium alloy was examined by the followingprocedure.

On a glass substrate, was deposited a metallic layer composed of analuminum-hafnium-chromium alloy to a thickness of 100 Å by thesputtering process using an aluminum-chromium-hafnium composite target.

The hafnium and chromium contents of the metallic layer thus formed wereeach 2 atom%.

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride, whereby corrosionresistance of the metallic layer was evaluated by measuring a change inreflectance of said metallic layer.

The reflectance of the metallic layer did not change before and afterthe immersion in the aqueous sodium chloride solution of said metalliclayer.

The number of pinholes observed in the metallic layer after theabove-mentioned immersion was less than 50 pieces (49 pieces) per unitsurface area (5 cm×5 cm).

EXAMPLE 6

On a substrate used in the Example 3, were deposited successively aprotective film (1100 Å in thickness) composed of Si₃ N₄ and a recordinglayer (260 Å in thickness) composed of Pt₁₀ Tb₂₉ Fe₅₅ Co₆ (atom %) bythe sputtering process, and thereon was deposited was deposited ametallic layer (500 Å in thickness) composed of an Al-Cr-Hf alloy by thesputtering process using a composite target of Al-Cr-Hf. The Cr and Hfcontents in the Al alloy (layer) constituting the metallic layerobtained were each 2 atom%.

The information recording medium obtained was held for about 720 hoursunder the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer for the recording layer were evaluated bymeasuring a change in reflectance of the information recording mediumand surface profile of the metallic layer.

The reflectance of the information recording medium did not changebefore and after holding the same under the circumstances of 80° C. anda relative humidity of 85%.

the optimum recording power of this information recording medium at alinear velocity of (5.7) m/sec was (3.6) mW, and the optimum recordingpower at a linear velocity of (11.3) m/sec was (5.3) mW.

EXAMPLE 7

On a substate used in the Example 3, were deposited successively aprotective film (1000 Å in thickness composed of Pt₁₀ Tb₂₉ Fe₅₅ Co₆ bythe sputtering process, and theroen was deposited a metallic layer (700Å in thickness) composed of an Al-Cr-Hf alloy by the sputtering processusing a composite target of Al-Cr-Hf. The Cr and Hf contents in the Alalloy (layer) constituting the metallic layer obtained were each 2atom%.

The information recording medium obtained was held for about 720 hoursunder the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer for the recording layer were evaluated bymeasuring a change in reflectance of the information recording mediumand surface profile of the metallic layer.

The reflectance of the information recording medium did not changebefore and after holding the same under the circumstances of 80° C. anda relative humidity of 85%.

Comparative Example 3

On a glass substrate, a metallic layer composed of an aluminum-chromiumalloy was formed to a thickness of 1000 Å by the sputtering processusing an aluminum-chromium composite target.

The chromium content of the metallic layer thus formed was 2 atom%.

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride.

After the 4-hour immersion, changes in reflectance and surface profileof the metallic layer were measured. The reflectance of the metalliclayer thus measured decreased by about 2%.

The number of pinholes observed on the metallic layer was about 70pieces per unit film surface area (5 cm×5 cm).

Comparative Example 4

A metallic layer containing 4 atom% of chromium was obtained in the samemanner as in Comparative Example 3 but using a composite target of analuminum-chromium alloy different in composition from the compositetarget used in Comparative Example 3.

This metallic layer was immersed in an aqueous sodium chloride solutionin the same way as in Comparative Example 3 to measure changes inrelfectance and surface profile of the metallic layer after theimmersion thereof.

The reflectance of the metallic layer did not change before and afterthe immersion in the aqueous sodium chloride solution of said metalliclayer, and the number of pinholes observed in the metallic layer afterthe immersion thereof was about 70 pieces per unit film surface area (5cm ×5 cm).

EXAMPLE 8

Hereinafter, corrosion resistance of the metallic layers composed of analuminum-hafnium-titanium alloy was examined.

On a glass substrate, a metallic layer composed of analumiunum-hafnium-titanium alloy was formed by the sputtering processusing a composite target of aluminum (Al)-hafnium(Hf)-titanium (Ti).

the titanium content of the metallic layer thus obtained was 1 atom%,and the hafnium content thereof was 2 atom%.

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride, whereby corrosionresistance of the metallic layer was evaluated by measuring a change inreflectance of said metallic layer and surface profile of said metalliclayer.

The reflectance of the metallic layer did not change before and afterthe immersion in the aqueous sodium chloride solution of said metalliclayer, and the number of pinholes observed in the metallic layer afterthe immersion thereof was less than 40 pieces (38 pieces) per unit filmsurface area (5 cm×5 cm).

EXAMPLE 9

A metallic layer containing 2 atom% of titanium and 1 atom% of hafniumwas obtained in the same manner as in Example 8 but using a compositetarget composed of an aluminum-titanium-hafnium alloy different incomposition from the composite target used in Example 8.

This metallic layer was immersed in the same manner as in Example 7 inthe aqueous sodium chloride solution to evaluate corrosion resistance ofthe metallic layer by measuring changes in reflectance and surfaceprofile of the metallic layer after the immersion thereof.

The reflectance of the metallic layer did not change before and afterthe immersion in the aqueous sodium chloride solution of said metalliclayer, and the number of pinholes observed in the metallic layer afterthe immersion was less than 40 pieces (33 pieces) per unit film surfacearea (5 cm×5 cm).

EXAMPLE 10

On a substrate used in the Example 3, were deposited successively aprotective film (1100 Å in thickness) composed of Si₃ N₄ and a recordinglayer (260 Å in thickness) composed of PT₁₀ Tb₂₉ Fe₅₅ Co₆ (atom %) bythe sputtering process, and thereon was deposited a metallic layer (500Å in thickness) composed of an Al-Hf-Ti alloy by the sputtering processusing a composite target of Al-Hf-Ti.

The information recording medium thus obtained was held for about 720hours under the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer were evaluated by measuring a change inreflectance of said information recording medium.

The reflectance of the information recording medium did not changebefore and after holding said recording medium under the circumstancesof 80° C. and a relative humidity of 85%.

The optimum recording power of this information recording medium at alinear velocity of (5.7) m/sec was (3.3) mW, and the optimum recordingpower at a linear velocity of (1.3) m/sec was (4.7) mW.

Comparative Example 5

A metallic layer containing 2 atom% of titanium was obtained in the samemanner as in Example 8 but using a composite target of aluminum-titaniumin place of aluminum-titanium-hafnium used in Example 8.

This metallic layer was immersed in the aqueous sodium chloride solutionin the same way as in Example 8 to evaluate corrosion resistance of themetallic layer by measuring changes in reflectance and surface profileof said metallic layer after the immersion thereof.

The reflectance of the metallic layer decreased by about 8% by theimmersion of said metallic layer.

The number of pinholes observed in the metallic layer was 51 pieces perunit film surface area (5 cm×5 cm).

Comparative Example 6

A metallic layer composed of an aluminum-titanium alloy containing 4atom% of titanium was formed in the same manner as in ComparativeExample 5.

This metallic layer was immersed in the same way as in Example 8 in theaqueous sodium chloride solution to evaluate corrosion resistance of themetallic layer by measuring changes in reflectance and surface profileof said metallic layer after the immersion thereof.

The reflectance of the metallic layer decreased by about 2% by theimmersion of said metallic layer.

The number of pinholes observed in the metallic layer was more than 115pieces per unit film surface area (5 cm×5 cm).

EXAMPLE 11

On a surface used in the Example 3, were deposited successively aprotective film (1000 Å in thickness) composed of Si₃ N₄ and a recordinglayer (500 Å in thickness) composed of Pt₁₀ Tb₂₉ Fe₅₅ Co₆ by thesputtering process, and thereon was deposited a metallic layer (700 Å inthickness) composed of an Al-Hf-Ti alloy by the sputtering process usinga composite target of Al-Hf-Ti.

The information recording medium thus obtained was held for about 720hours under the circumstances of 80° C. and a relative humidity of 85%,whereby corrosion resistance of the metallic layer and protectivefunction of the metallic layer were evaluated by measuring a change inreflectance of said information recording medium.

The reflectance of the information recording medium did not changebefore and after holding said recording medium under the circumstancesof 80° C. and a relative humidity of 85%.

EXAMPLE 12

On a glass substate, a metallic layer (1000 Å in thickness) composed ofan aluminum-hafnium-magnesium alloy was formed by the sputtering processusing a composite target of aluminum (Al)-hafnium (Hf)-magnesium (Ng).

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride, whereby corrosionresistance of the metallic layer was evaluated by measuring a change inreflectance of said metallic layer and surface profile of said metalliclayer.

The reflectance of the metallic layer did not change before and afterthe immersion in the aqueous sodium chloride solution of said metalliclayer, and the number of pinholes observed in the metallic layer wasless than 30 pieces (25 pieces) per unit film surface area (5 cm×5 cm).

EXAMPLES 13-14

Metallic layers were formed in the same manner as in Example 12 butusing composite targets as shown in Table 1. The atom content and thenumber of pinholes of the metallic layers thus formed are shown in Table1.

    ______________________________________                                                Composite                                                                     target used                                                                   and                                                                           Composition                                                                              Atom content                                                       of Metallic                                                                              (at %)      Number of                                              layer      Mg     Hf     Ti  pinholes                                 ______________________________________                                        Example 12                                                                              Al--Mg--Hf    4     4    --  not more                                                                      than                                                                          30 pieces                                                                     (25 pieces)                            Example 13                                                                              Al--Mg--Hf   4      2    --  not more                                                                      than                                                                          30 pieces                                                                     (30 pieces)                            Example 14                                                                              Al--Mg--Hf--Ti                                                                             4      2    1   Less than                                                                     30 pieces                                                                     (30 pieces)                            Comparative                                                                             Al--Mg       5      --   --  70 pieces                              Example 7                                                                     ______________________________________                                    

EXAMPLE 15

On a substrate used in Example 3, were deposited successively aprotective film (1100 Å in thickness) composed of Si₃ N₄, and arecording layer (260 Å in thickness) composed of Pt₁₀ Tb₂₉ Fe₅₅ Co₆,(atom %) by the sputtering process, and was deposited thereon a metalliclayer (500 Å in thickness) composed of an Al-Mg-Hf alloy by thesputtering process using a composite target of aluminum (Al)-hafnium(Hf)-magnesium (Mg). The Mg content was 4 atom% and the Hf content was 2atom% in the Al alloy (layer) constituting the metallic layer as formedabove.

The information recording medium thus obtained was held for about 720hours under the circumferences of 80° C. and a relatively humidity of85%.

The reflectance of the information recording medium did not changebefore and after holding the information recording medium under thecircumstances of 80° C. and a relative humidity of 85%.

The optimum recording power of this information recording medium at alinear velocity of (5.7) m/sec was (4.0) mW, and the optimum recordingpower at a linear velocity of (11.3) m/sec was (5.6) mW.

Comparative Example 7

On a glass substrate, was formed a metallic layer (1000 Å thickness)composed of an aluminum-magnesium alloy by the sputtering process usinga composite target of aluminum-magnesium.

The magnesium content in the metallic layer thus obtained was 5 atom%.

This metallic layer was immersed for 4 hours at 60° C. in an aqueoussolution containing 10% by weight of sodium chloride.

The reflectance of the metallic layer immersed decreased by about 2% bythe above-mentioned immersion.

The number of pinholes observed in the metallic layer was about 70pieces per unit film surface area (5 cm×5 cm).

What is claimed is;
 1. In an information recording medium having asubstrate and thereon an optical recording layer and a metallic layer,the improvement which resides in that the metallic layer is composed ofan aluminum alloy containing 0.1-9.5 atom% of hafnium and 0.1-5 atom% ofchromium based on all atoms constituting aluminum alloy, the combinedcontent of said hafnium and chromium being less than 10 atom%.
 2. In aninformation recording medium having a substrate and thereon an opticalrecording layer and a metallic layer, the improvement which resides inthat the metallic layer is composed of an aluminum alloy containing0.1-9.5 atom% of hafnium, 0.1-5 atom% of chromium and 0.1-9.5 atom% oftitanium based on all atoms constituting aluminum alloy, the combinedcontent of said hafnium, chromium and titanum being less than 10 atom%.3. In an information recording medium having a substrate and thereon anoptical recording layer and a metallic layer, the improvement whichresides in that the metallic layer is composed of an aluminum alloycontaining 0.5-5 atom% of hafnium and 0.5-5 atom of titanium based onall atoms constituting aluminum alloy, the combined content of saidhafnium and titanium being 1-5.5 atom%.
 4. In an information recordingmedium having a substrate and thereon an optical recording layer and ametallic layer, the improvement which resides in that the metallic layeris composed of an aluminum alloy containing 0.1-10 atom% of hafnium and0.1-10 atom% of magnesium based on all atoms constituting aluminumalloy, the combined content of said hafnium and magnesium being lessthan 15 atom%.
 5. In an information recording medium having a substrateand thereon an optical recording layer and a metallic layer, theimprovement which resides in that the metallic layer is composed of analuminum alloy containing 0.1-10 atom% of hafnium, 0.1-10 atom% ofmagnesium and 0.1-10 atom% of titanium based on all atoms constitutingaluminum alloy, the combined content of said hafnium, mangesium andtitanium being less than 15 atom%.
 6. In an information recording mediumhaving a substrate and thereon an optical recording layer and a metalliclayer, the metallic layer is composed of an aluminum alloy containing0.1-10 atom% of hafnium, 0.1-10 atom of magnesium and not more than 10atom% of chromium based on all atoms constituting aluminum alloy, thecombined content of said hafnium, magnesium and chromium being less than15 atom%.
 7. In an information recording medium having a substrate andthereon an optical recording layer and a metallic layer, the improvementwhich resides in that the metallic layer is composed of an aluminumalloy containing 0.1-10 atom% of hafnium, 0.1-10 atom% of magnesium and0.1-10 atom% of titanium and less than 10 atom% of chromium based on allatoms constituting aluminum alloy, the combined content of said hafnium,magnesium, titanium and chromium being less than 15 atom%.
 8. Theinformation recording medium as claimed in any one of claims 1-7 whereinthe recording layer is a magnetooptical recording layer.
 9. Theinformation recording medium as claimed in any one of claims 1-7 whereinthe metallic layer has a film thickness of 100-5000 Å.